Steadying resistance for electric lamps.



No. 743,028. PATENTED NOV. 3, 1903.

. H. N. POTTER.

STBADYING RESISTANCE FOR ELECTRIC LAMPS.

APPLICATION FILED AUG.9.1899.

N0 MODEL.

UNITED STATES v,

Patented November 3, 1903.

PATENT OFFICE.

HENRY NOEL POTTER, OF GOTTINGEN, GERMANY, ASSIGNOR TO GEORGE WESTINGHOUSE, OF PITTSBURG, PENNSYLVANIA.

STE-ADYING RESISTANCE FOR ELECTRIC LAMPS.

SPECIFICATION forming part of Letters Patent No. 743,028, dated November 3, 1903.

Application filed August 9, 1899. Serial No. 726 617. (N0 model.)

To aZZ whom it may concern.-

Be it known that I, HENRY NOEL POTTER, a citizen of the United States of America, and a resident of Gottingen, Germany, have invented certain new and useful Improvements in Steadying Resistances for Electric Lamps, of which the following is a specification.

It is found in practice that as the current through a glower formed of one or more dry electrolytes is increased the voltage across its terminals rises at first rapidly and then more and more slowly to a maximum, beyond which it drops off and falls with increasing rapidity as the efficiency of the glower as a light giving body increases. Beyond the point of maximum voltage the decrease in the resistance of the glower is so rapid as to make the circuit difficult to control, while it is also found difficult to operate glowers directly on a constant-potential commercial circuit even at a lower efficiency than that at which the voltage is maximum, because no commercial potential can be quite constant at the lamp-terminals and slight variations of voltage are accompanied by relatively large variations in current and light. It is therefore customary to provide each glower with a ballast resistance, so as to counteract the decreasing resistance of the glower by the increase in its own drop as the current through glower and ballast increases.

I have found that different materials employed as ballast resistances exercise corrective effects in different degrees, and for each material there is a region of temperature within which a given percentage increase of current produces a maximum increase in resistance. This region of temperature I call the critical region of each material. It is desirable that the material of the ballast should have as large a corrective effect as possible, so that for each per cent. increase in current there should be a large increase in drop at the ballast, and it is desirable that the specific resistance of the ballast when operating normally should be as large as possible, so that the actual length of ballast-conductor may be as small as possible. This may be advantageously secured in the case of any particular conductor by operating it at as high a temperature as is practicable. It is thus desirable that the critical region should lie at a high temperature. The advantages arising from the last-named condition are, in addition to that already men tioned, first, that the hot running ballast is less influenced by changes in the surrounding temperature and there is less necessity of providing it with ventilation; second, that it has less weight, owing to its greater specific resistance, and therefore less specific heat, so that it changes its temperature more rapidly with changes of current than would be the case were its specific heat greater. I find that iron most nearly approaches the ideal material for ballast resistances. Comparing it with platinum, for example, I find that the latter metal shows a maximum correction of about twenty-five per cent. for ten per cent. increase in current, whereas iron shows a maximum correction of two hundred per cent. or over for the same percentage increase of current. Nickel,which hasalarger maximum correction than platinum, eifects this correction at such a low temperature and has at that temperature such a low specific resistance as to necessitate the employment of a comparatively great length of conductor for a given drop, and consequently one that has a great Weight of material and which renders the device comparatively sluggish in its action. Owing to the fact that iron when exposed to the atmosphere oxidizes readily, I inclose the iron ballast in a small chamber filled with a gas which does notattackiron. Thus disposed within a chamber the ballast becomes very easy of transportation and handling and may without inconvenience be secured in its place in the circuit of the lamp. I usually employ hydrogen gas in the chamber, as I find that the chamber ballast-wire does not deteriorate appreciably, so that practically it may be relied upon to last until its life is terminated by accident. Hydrogen, in addition to not injuring the ballast-conductor, has the advantage over other gases of conducting heat exceptionally well, so that a given number of watts may be dissipated from a smaller surface of ballast-wire than if the same were surrounded by an atmosphere of other gas.

The ballast-wire is so proportioned as to be brought nearly to a red heat by the normal operating-current for the glower,the material of the ballast resistance and its form and dimensions being such that the condition above specified is characteristic of that region of working in which a maximum corrective effeet is obtained and which I term the critical region.

In the accompanying drawings I have illustrated the application of myinvention in Figure 1. Figs. 2 and 3 illustrate modifications.

Referring to the drawings, G represents a glower composed of rare earthssuch, for instance, as zirconia and yttria or mixtures thereof properly prepared and formed into suitable shapes for illuminating purposes. For the purpose of imparting the preliminary heat to the glower to raise it to a conducting temperature a heating-coil A of suitable form is employed. In the drawings I have represented diagrammatically a coil of fine platinum wire placed in the immediate vicinity of the glower. It may be mounted upon any suitable support and capable of being moved to or from the glower in any convenient manner, or it may occupy a fixed position with reference to the glower.

In the drawings I have shown the steadying resistance orbalancing device B connected in series with the glower G. This device consists of a length l) of pure or approximately pure iron inclosed within a tube 1), which may be of any suitable material which will exclude the air, a glass tube being usually employed. The air is exhausted from this tube and an inert gas, preferably hydrogen, is introduced in place of the air, the primary object being to exclude any gas which will attack the iron when heated. Other gases having the proper characteristics may be employed; but I have obtained the best results from the use of hydrogen, as it is usually obtainable in a pure or nearly pure state, is inert with reference to iron, and is a relatively good conductor of heat.

In general the amount of current flowing through an iron ballast-wire that is surrounded by an atmosphere of hydrogen and subject to a constant difference of electric potential increases as the density of the atmosphere increases. This characteristic may be utilized for securing the desired electrical resistance of the balancing device, if desired; but for ordinary work little or no adjustment is required and it is usual to introduce hydrogen at about atmospheric pressure and then seal the tubes.

The best results are usually obtained with ballast-conductors made of pure iron-such, for instance,as that obtained electrolytically. I do not, however, limit myself to the use of pure iron, since slight impurities may sometimes exist Without materially interfering with the results.

In the drawings I have shown the balancing-conductor as connected in series with the glower, the heater being connected in shunt upon the glower and balancing-coil. The current of the heating-coil may, however, be obtained from any suitable source other than the source of the current for operating the lamp. I have also shown the heating-circuit provided with an automatic circuit-interrupting device D, comprising a solenoid (Z and core d, operating a circuit-breaking point 01 This solenoid is included in the circuit of the glower, so that when an operating-current is flowing through the glower 'the solenoid draws the core d within itself,

and thus opens the circuit of the heater.

The ends of the iron strip or wire are usually connected to wires of platinum or other suitable metal, which are sealed into the ends of the tube, the sealing being done in the same general manner as that employed in sealing leading-in wires into an ordinaryincandescent lamp and the platinum being used for the samereason. Anyother suitable material for leading-in wires may, however, be employed.

In cases where large currents are to be em ployed for operating the lamp it may be desirable to use several of these devices connected in parallel with each other, but in series with the glower, as shown at B B B in Fig. 2, for instance. This arrangement permits of the use of smaller leading-in wires than would be necessary if all of the current which is to pass to the glower were to pass through a single balancing device. Instead of making several separate balancing devices Isometimes connect two or more lengths of iron in parallel with each other within the same inclosing chamber, as indicated at b b b b in Fig. 3.

It will be understood that while I have described an electric lamp provided with an electric heating device forming part of the same lamp the advantages of the iron balancing device would also be present in a lamp adapted to be brought to its operative condition by a torch or some other source of heat.

I claim as my invention- 1. The combination with a lamp-glower composed of one or more dry electrolytes and the effective resistance of which decreases with increments of temperature, of a balancing device consisting of a material or compo sition having a critical region within which its resistance automatically increases abnormally with increments of temperature.

2. The combination with a lampglower adapted to be highly heated by an electric current and to decrease in resistance as the temperature increases, of a resistance in circuit with the glower, the said resistance being maintained at approximately a red heat by the normal operating-current of the lamp.

3. The combination with a lamp-glower composed of materials which are non-conductive when cold and conductive when heated and having the characteristic of decreasing in resistance with increments of temperature and of becoming incandescent at a very high temperature, of a steadying resistance or hallast device consisting of iron wire in series with the glower and so proportioned as to be heated by the glower-current to a temperature at which its resistance increases abnormally with increments of temperature.

4. The combination with a lamp-glower composed of materials which are non-conductive when cold and conductive when heated and having the characteristic of decreasing in resistance with increments of temperature and of becoming incandescent at a very high temperature, of a steadying resistance or ballast device consisting of iron wire in series with the glower, and an airtight inclosing chamber therefor.

5. The combination with a lamp glower composed of materials which are non-conductive when cold and conductive when heated and having the characteristic of decreasing in resistance with increments in temperature and of becoming incandescent at a very high temperature, of a steadying resistance or ballast device consisting of a length of iron wire in series with the glower and so proportioned as to be heated by the normal glower-current to a temperature at which its resistance increases abnormally with increments of temperature.

6. In an incandescent lamp, the combination with a glower that becomes conductive only when heated, of a ballast-conductor in series with the glower the resistance of which increases at an abnormally high rate when traversed by currentthat is greater than the normal maximum for the glower.

7. The combination with a lamp-glower composed of materials which are non-conductive when cold and conductive when heated and have the characteristic of decreasing in resistance with increments of increase in temperature and of becoming incandescent at a high temperature, of a balancing device in series with the glower the resistance of which is automatically increased to an abnormal extent by a slight increase of current above the normal.

8. The combination with a lampglower adapted to be highly heated by the passage of an electric current, of a balancing device having a critical region within which its resistance is automatically increasable to an abnormal extent by a slight increase of current, the critical region overlapping the points which lie at the normal operating-voltage of the lamp and extending above the same.

9. A balancing device for electric lamps consisting of a length of iron, a hermeticallysealed chamber containing the same, and within which the iron is surrounded by an atmosphere of hydrogen.

10. The combination with a glower for lamps consisting of a material or materials which are non-conductive when cold and conductive when heated, of a balancing device in series therewith, composed of iron wire so proportioned as to be heated by the glowercurrent to a temperature at which its resistance increases abnormally with increments of temperature, a heating device for the glower consisting of an electric conductor connected in shunt from the glower and the balancing device, and means for interrupting the circuit connections through the heating device.

11. The combination with a glower for lamps composed of a dry electrolyte or dry electrolytes,and whose effective resistance decreases with increments in temperature, of a balancing device consisting of an iron conductor, and a hermetically-sealed inclosing chamber therefor from which air is excluded.

12. The combination with a glower formed from a material which is a non conductor when cold and a conductor when heated to the proper temperature, of a balancing device consisting of a length of iron, and a chamber inclosing the same containing an inert gas.

13. A balancing device for electric lamps consisting of a length of iron, an air-tight chamber inclosing the same and containing an inert gas, in combination with terminals of platinum sealed in the ends of the chamber.

14. The combination with a lamp-glower composed of one or more dry electrolytes and whose effective resistance decreases with increments of temperature, of a balancing device consisting of a material or composition having a critical region within which its resistance automatically increases abnormally with increments of current.

15. In an incandescent lamp, the combination of a pencil or body adapted to be highly heated by the passage of an electric current, and a resistance automatically increasable to an abnormal extent by a slight increase of current abovelthe normal, connected in series with the pencil, substantially as set forth.

16. In an incandescent lamp, the combination of a pencil or body adapted to be highly heated by an electric current, and a circuit therefor, a portion of said circuit being formed by a conductor adapted to carry a normal current without material change and to present abnormally increasing resistance on a slight increase of current above the normal in the circuit, substantially as set forth.

HENRY NOEL POTTER.

Witnesses:

W. H. ANDERSON, KIRKE LATHROP. 

